Testing Providers with PyWBEM

Transcription

1 Testing Providers with PyWBEM Tim Potter Hewlett-Packard 2006 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice

2 Overview PyWBEM basics Exploring with wbemcli.py Unit testing with unittest module Async client programming with Twisted Using the MOF compiler Presentation materials available at November 2008

3 PyWBEM overview A pure-python library for WBEM Sync and async CIM-XML client Provider interface MOF compiler Command line client Uses Python language features to provide easy to use interfaces for WBEM 3 18 November 2008

4 Getting started Install PyWBEM Available in some distros Create connection WBEMConnection() for CIM-XML over http/https {Pegasus,OpenWBEM,SFCB}UDSConnection() for unix domain socket access Use connection object to perform operations and return other PyWBEM objects 4 18 November 2008

5 pywbem.ciminstancename Represents an object path/model path Attributes host classname namespace keybindings Use Python object attributes and dictionary interface 5 18 November 2008

6 pywbem.ciminstance Represents an instance of a class Attributes host classname namespace path (is a CIMInstanceName) properties Use Python object attributes and dictionary interface 6 18 November 2008

7 Error handling Python exception is thrown when a CIM error occurs try: cli.enumerateinstances('cim_foo') except pywbem.cimerror, arg: error = arg[0] # error number description = arg[1] # string Error constants available, e.g CIM_ERR_FAILED 7 18 November 2008

8 Other useful objects CIMClass classname properties, methods, qualifiers CIMDateTime Wrapper for datetime.{datetime,timedelta} CIM numeric types SintXX, UintXX, RealXX CIMQualifier name, value, type 8 18 November 2008

9 Demo #1 and #2 Making connections Performing simple WBEM operations Accessing CIM object attributes 9 18 November 2008

10 Testing Instance Providers EnumerateInstanceNames(ClassName) List of CIMInstanceName EnumerateInstances(ClassName) List of CIMInstance GetInstance(InstanceName) List of CIMInstance ModifyInstance(Instance) None DeleteInstance(InstanceName) None CreateInstance(Instance) CIMInstanceName November 2008

11 Testing Association Providers AssociatorNames(InstanceName, Args...) List of CIMInstanceName Associators(InstanceName, Args...) List of CIMInstance ReferenceNames(InstanceName, Args...) List of CIMInstanceName References(InstanceName, Args...) List of CIMInstance Arguments are ResultClass, Role, AssociationClass, etc November 2008

12 Testing Method Providers InvokeMethod(MethodName, InstanceName, InParams) Tuple of method result and output parameters Result, OutParams = cli.invokemethod( 'SetPowerState', cs, PowerState = pywbem.uint32(8), Time = datetime.now()) November 2008

13 wbemcli.py Command line tool for exploration and ad-hoc testing Connects to a WBEM server then drops into Python interactive interpreter Lots of extra goodies to make life easier for testing and debugging November 2008

14 wbemcli.py (cont) Usage: wbemcli.py HOST [ u USER] [ p PASS] \ [ n NAMESPACE] [ no ssl] [ port PORT] Features Uses full power of Python interactive interpreter Saves command line history to disk Aliases for common WBEM operations Pretty print of long results November 2008

15 Demo #3 Using wbemcli.py for ad-hoc testing November 2008

16 Unit testing with unittest.py Built-in unit testing module using xunit interface setup(), runtest(), teardown() Test fixtures created for each test case Python version clunky but still usable Can run tests individually By named test case By named test method November 2008

17 Demo #4 Running unit tests based on Python's unittest.py module November 2008

18 Asynchronous client programming Uses Twisted Python networking framework Event driven programming model no threads reactor is central object in a Twisted program Uses callback model to respond to events defered is central object for using callbacks Go read tutorial and reference documentation at November 2008

19 Using the PyWBEM Twisted Client Basic process for performing a client operation: 1. Create a factory which creates instances of the operation you want to perform 2. Add callbacks 3. Call reactor.connecttcp() 4. Enter or return to event loop Return deferred objects to hang callbacks off A deferred is a promise that a function will at some point have a result November 2008

20 Example: Create CIM_Indication filter CIM operations, twisted style Create CIMInstance object Create a CreateInstance factory Add success and failure callbacks Make TCP client connection Enter event loop Trigger subsequent operations off callbacks November 2008

21 Creating a CIM Listener Basic process for listening for indications Create a twisted.web.server listening on port 5988 and port 5989 Create a twisted.web.resource to handle POST requests and parse received XML Call reactor.listentcp() function or reactor.listenssl() See irecv.py file in PyWBEM distribution Can have CIM client and server in same process November 2008

22 Using PyWBEM MOF Compiler Define a class with a PyWBEM server interface CreateClass, ModifyClass, EnumerateQualifiers, etc Create a mof_compiler.mofcompiler instance Call compile_file() for each MOF file to process November 2008

23 Tricks & Traps Use DeepInheritance = True when enumerating classes and class names Use LocalOnly = False when calling GetClass() method Watch out for host attribute in return values from associators May need to set to None November 2008

24 24 18 November 2008